Several techniques for extracting metal species are commonly used in the metals industry. In particular, in the case where the extracted ores have a low metal derivative content, leaching techniques are used consisting of extracting the soluble metal portions by leaching using a suitable solubilizing agent. Once the metal derivatives are dissolved in ionic form, a subsequent step consists of separating the species of interest from the impurities or other pollutants.
The separation processes are characterized by putting one or several liquid phases (called “mobile”) in contact with a solid phase (called “stationary”). The ionic metal derivative injected into the liquid phase establishes one or several interactions of various natures with the stationary phase as is the case in ion exchange chromatography. Its displacement within the chromatographic device is therefore different from the displacement of other products contained in the load to be processed. Based on this difference in interactions, it is possible to purify or enrich one of the fractions with the ionic metal derivative.
Processes have been proposed to carry out the continuous ion exchange. U.S. Pat. No. 2,815,332 describes a closed-circuit system in which the resin progresses in the reverse direction of flow from the liquid. This loop contains four zones isolated by valves and dedicated to saturation, rinsing, regeneration and rinsing, respectively. The resin progresses in the zones and from one compartment to the next, in the reverse direction of flow from the liquid phase, under the effect of hydraulic pulsations.
Certain authors have developed, for chromatography, a system called SMB (Simulated Moving Bed). Thus, U.S. Pat. No. 2,985,589 describes a continuous chromatography process, SMB, in which the chromatography resin is fixed, distributed in several compartments, but its movement is simulated by the movement at regular intervals of the position of the fluid inlets and outlets. The inlet positions (feed and eluent) and outlet positions (extract and raffinate) then define four zones. U.S. Pat. No. 6,375,851 describes a system with six zones, adaptation of the ion exchange of the process previously described in U.S. Pat. No. 2,985,589. The system described in U.S. Pat. No. 6,375,851 is based on a SMB, except for the regeneration step, which is implemented with a front movement. The fluid inlets and outlets are therefore offset, generally simultaneously, synchronously after a sequence. In all of these systems, the authors provide for completely continuity of circulation of all of the fluids. These systems lead to a very significant number of columns, the size of the columns being defined by the smallest sequence of the sequential.
For processes applied in hydrometallurgy, and in particular ion exchange processes as is the case in WO 2007/087698, the production and regeneration steps are systematically followed by rinsing steps. In batch processes, the steps are most often done at the optimal rate relative to the fixing or desorption kinetics. Thus current techniques do not make it possible to perform a large-scale separation process that is economically advantageous, because it requires excessively high quantities of resin for the columns and processing products. This drawback is even more true given that no process currently used makes it possible to perform the entire processing cycle continuously, in particular at the regeneration step of the resins. Added to this drawback is the fact that all of these methods involve the use of very significant quantities of water, in mining regions that are generally located in desert areas, as well as significant quantities of regenerant, which are in most cases highly acidic. In addition to the economic problems, then, one is also faced with ecological problems and the protection of environmental resources.